Transitional Spectral Behavior in Blazar OJ 287: A Comprehensive Multi-Epoch SED Study

TL;DR

This study provides a detailed multi-epoch spectral energy distribution analysis of blazar OJ 287, revealing flux-dependent spectral transitions and correlations among emission components across different activity states.

Contribution

It introduces a comprehensive multi-wavelength dataset and models the transitional spectral behavior of OJ 287, highlighting the evolution of emission mechanisms during different flux states.

Findings

Flux variability observed across optical-UV, X-ray, and gamma-ray bands.

Strong correlations among optical, UV, and X-ray fluxes, but not with gamma-ray.

Spectral states transition from inverse Compton dominance in quiescent states to synchrotron dominance during flares.

Abstract

We present a comprehensive multi-wavelength investigation of BL Lac object OJ 287 using Swift and Fermi observatories spanning 2008-2025. The source exhibits significant flux variability across optical-UV, X-ray, and $\gamma$-ray regimes, with outbursts observed in optical, UV and X-ray frequencies. Variability and correlation analyses of the long-term lightcurves reveal strong correlations among optical, UV, and X-ray bands, whereas there is no significant correlation between $\gamma$-ray and other bands. Using a decade-long dataset (MJD 57382-60448), we analysed X-ray spectral variability across different flux states (flare, intermediate, and quiescent). Multi-wavelength spectral energy distributions (SEDs) were constructed using a one-zone leptonic model to investigate the transitional nature of the X-ray spectral position in the broadband. The analysis reveals OJ 287's consistent flux-dependent transitional spectral behavior: quiescent states show hard X-ray spectra dominated by inverse Compton emission; intermediate states exhibit contributions from both inverse Compton and synchrotron components with moderately hard spectra; flaring events are characterized by predominantly synchrotron emission, resulting in soft X-ray spectra. Broadband SED modelling captures the systematic evolution of model parameters across different activity states, with correlation analysis revealing strong positive correlations between synchrotron peak frequency, Synchrotron-Self Compton peak frequency, and X-ray flux, providing quantitative evidence for the changing dominance of emission components within the blazar's relativistic jet.